Liquid crystal composition and liquid crystal display device

ABSTRACT

A liquid crystal composition satisfying at least one characteristic such as high maximum temperature of a nematic phase, low minimum temperature thereof, small viscosity, suitable optical anisotropy, large negative dielectric anisotropy, large specific resistance, high stability to ultraviolet light, heat or the like, or having a suitable balance regarding at least two of the characteristics; and an AM device having characteristics such as short response time, a large voltage holding ratio, low threshold voltage, a large contrast ratio and a long service life. The liquid crystal composition contains a compound that can contribute to high stability to heat or ultraviolet light, has negative dielectric anisotropy and the nematic phase.

TECHNICAL FIELD

The invention relates to a liquid crystal composition, a liquid crystaldisplay device including the composition and so forth. In particular,the invention relates to a liquid crystal composition having a negativedielectric anisotropy, and a liquid crystal display device that includesthe liquid crystal composition and has a mode such as an IPS mode, a VAmode, an FFS mode and an FPA mode. The invention also relates to aliquid crystal display device having a polymer sustained alignment mode.

BACKGROUND ART

In a liquid crystal display device, a classification based on anoperating mode for liquid crystal molecules includes a phase change (PC)mode, a twisted nematic (TN) mode, a super twisted nematic (STN) mode,an electrically controlled birefringence (ECB) mode, an opticallycompensated bend (OCB) mode, an in-plane switching (IPS) mode, avertical alignment (VA) mode, a fringe field switching (FFS) or a fieldinduced photo-reactive alignment (FPA) mode. A classification based on adriving mode in the device includes a passive matrix (PM) and an activematrix (AM). The PM is classified into static and multiplex and soforth. The AM is classified into a thin film transistor (TFT), a metalinsulator metal (MIM) and so forth. The TFT is further classified intoamorphous silicon and polycrystal silicon. The latter is classified intoa high temperature type and a low temperature type based on a productionprocess. A classification based on a light source includes a reflectivetype utilizing natural light, a transmissive type utilizing backlightand a transflective type utilizing both the natural light and thebacklight.

The liquid crystal display device includes a liquid crystal compositionhaving a nematic phase. The composition has suitable characteristics. AnAM device having good characteristics can be obtained by improvingcharacteristics of the composition. Table 1 below summarizes arelationship of the characteristics between two aspects. Thecharacteristics of the composition will be further described based on acommercially available AM device. A temperature range of the nematicphase relates to a temperature range in which the device can be used. Apreferred maximum temperature of the nematic phase is about 70° C. orhigher, and a preferred minimum temperature of the nematic phase isabout −10° C. or lower. Viscosity of the liquid crystal compositionrelates to a response time of the device. A short response time ispreferred for displaying moving images on the device. A shorter responsetime even by one millisecond is desirable. Accordingly, a smallviscosity of the composition is preferred. A small viscosity at a lowtemperature is further preferred.

TABLE 1 Characteristics of Composition and AM Device No. Characteristicsof Composition Characteristics of AM Device 1 Wide temperature range ofa Wide usable temperature nematic phase range 2 Small viscosity¹⁾ Shortresponse time 3 Suitable optical anisotropy Large contrast ratio 4 Largepositive or negative Low threshold voltage and dielectric anisotropysmall electric power consumption Large contrast ratio 5 Large specificresistance Large voltage holding ratio and large contrast ratio 6 Highstability to ultraviolet light Long service life and heat ¹⁾A liquidcrystal composition can be injected into a liquid crystal display devicein a short time.

An optical anisotropy of the composition relates to a contrast ratio inthe device. According to a mode of the device, a large opticalanisotropy or a small optical anisotropy, more specifically, a suitableoptical anisotropy is required. A product (Δn×d) of the opticalanisotropy (an) of the composition and a cell gap (d) in the device isdesigned so as to maximize the contrast ratio. A suitable value of theproduct depends on a type of the operating mode. The suitable value isin the range of about 0.30 micrometer to about 0.40 micrometer in adevice having the VA mode, and is in the range of about 0.20 micrometerto about 0.30 micrometer in a device having the IPS mode or the FFSmode. In the above cases, a composition having the large opticalanisotropy is preferred for a device having a small cell gap. A largedielectric anisotropy in the composition contributes to a low thresholdvoltage, a small electric power consumption and a large contrast ratioin the device. Accordingly, the large dielectric anisotropy ispreferred. A large specific resistance in the composition contributes toa large voltage holding ratio and the large contrast ratio in thedevice. Accordingly, a composition having the large specific resistanceat room temperature and also at a high temperature in an initial stageis preferred. The composition having the large specific resistance atroom temperature and also at a high temperature after the device hasbeen used for a long period of time is preferred. Stability of thecomposition to ultraviolet light and heat relates to a service life ofthe liquid crystal display device. In the case where the stability ishigh, the device has a long service life. Such characteristics arepreferred for an AM device used in a liquid crystal projector, a liquidcrystal television and so forth.

In a liquid crystal display device having a polymer sustained alignment(PSA) mode, a liquid crystal composition containing a polymer is used.First, a composition to which a small amount of a polymerizable compoundis added is injected into the device. Then, the composition isirradiated with ultraviolet light while voltage is applied betweensubstrates of the device. The polymerizable compound is polymerized toform a network structure of the polymer in the liquid crystalcomposition. In the composition, alignment of liquid crystal moleculescan be controlled by the polymer, and therefore the response time of thedevice is shortened and also image persistence is improved. Such aneffect of the polymer can be expected for a device having the mode suchas the TN mode, the ECB mode, the OCB mode, the IPS mode, the VA mode,the FFS mode and the FPA mode.

A composition having a positive dielectric anisotropy is used for an AMdevice having the TN mode. In an AM device having the VA mode, acomposition having a negative dielectric anisotropy is used. Acomposition having the positive or negative dielectric anisotropy isused for an AM device having the IPS mode or the FFS mode. In an AMdevice of the polymer sustained alignment (PSA) mode, a compositionhaving the positive or negative dielectric anisotropy is used. Compound(1) of the invention is disclosed in Patent literature No. 1, an exampleof a liquid crystal composition having the negative dielectricanisotropy is disclosed in Patent literature Nos. 2 and 3.

CITATION LIST Patent Literature

Patent literature No. 1: JP 2004-507607 A.

Patent literature No. 2: EP 2463355 A.

Patent literature No. 3: WO 2012-076105 A.

SUMMARY OF THE INVENTION Technical Problem

One of aims of the invention is to provide a liquid crystal compositionsatisfying at least one of characteristics such as a high maximumtemperature of a nematic phase, a low minimum temperature of the nematicphase, a small viscosity, a suitable optical anisotropy, a largenegative dielectric anisotropy, a large specific resistance, a highstability to ultraviolet light and a high stability to heat. Another aimis to provide a liquid crystal composition having a suitable balanceregarding at least two of the characteristics. Another aim is to providea liquid crystal display device including such a composition. Anotheraim is to provide an AM device having characteristics such as a shortresponse time, a large voltage holding ratio, a low threshold voltage, alarge contrast ratio and a long service life.

Solution to Problem

The invention concerns a liquid crystal composition that has a negativedielectric anisotropy and a nematic phase, and contains at least onecompound selected from the group of compounds represented by formula (1)as an additive, and at least one compound selected from the group ofcompounds represented by formula (2) as a first component, and a liquidcrystal display device including the composition:

wherein, in formula (1) and formula (2), R¹ and R² are independentlyhydrogen or alkyl having 1 to 15 carbons; R³ and R⁴ are independentlyalkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons, alkenylhaving 2 to 12 carbons or alkenyloxy having 2 to 12 carbons; ring A andring C are independently 1,4-cyclohexylene, 1,4-cyclohexenylene,1,4-phenylene, 1,4-phenylene in which at least one of hydrogen isreplaced by fluorine or chlorine, or tetrahydropyran-2,5-diyl; ring B is2,3-difluoro-1,4-phenylene, 2-chloro-3-fluoro-1,4-phenylene,2,3-difluoro-5-methyl-1,4-phenylene, 3,4,5-trifluoronaphthalene-2,6-diylor 7,8-difluorochroman-2,6-diyl; Z¹ is alkylene having 1 to 20 carbons,and in the alkylene, at least one of hydrogen may be replaced byhalogen, and at least one of —CH₂— may be replaced by —O—; Z² and Z³ areindependently a single bond, ethylene, methyleneoxy or carbonyloxy, andwhen all of Z² are a single bond, R³ is alkenyl having 2 to 12 carbonsor alkenyloxy having 2 to 12 carbons; and a is 1, 2 or 3, b is 0 or 1,and a sum of a and b is 3 or less.

Advantageous Effects of Invention

An advantage of the invention is a liquid crystal composition satisfyingat least one of characteristics such as a high maximum temperature of anematic phase, a low minimum temperature of the nematic phase, a smallviscosity, a suitable optical anisotropy, a large negative dielectricanisotropy, a large specific resistance, a high stability to ultravioletlight and a high stability to heat. Another advantage is a liquidcrystal composition having a suitable balance regarding at least two ofthe characteristics. Another advantage is a liquid crystal displaydevice including such a composition. Another advantage is an AM devicehaving characteristics such as a short response time, a large voltageholding ratio, a low threshold voltage, a large contrast ratio and along service life.

DESCRIPTION OF EMBODIMENTS

Usage of terms herein is as described below. Terms “liquid crystalcomposition” and “liquid crystal display device” may be occasionallyabbreviated as “composition” and “device,” respectively. The liquidcrystal display device is a generic term for a liquid crystal displaypanel and a liquid crystal display module. A liquid crystal compound isa generic term for a compound having a liquid crystal phase such as anematic phase and a smectic phase, and a compound having no liquidcrystal phase but to be mixed with a composition for the purpose ofadjusting characteristics such as a temperature range of the nematicphase, viscosity and dielectric anisotropy. The compound has asix-membered ring such as 1,4-cyclohexylene and 1,4-phenylene, and rodlike molecular structure. A polymerizable compound is added for thepurpose of forming a polymer in the composition.

The liquid crystal composition is prepared by mixing a plurality ofliquid crystal compounds. A ratio (content) of the liquid crystalcompounds is expressed in terms of weight percent (% by weight) based onthe weight of the liquid crystal composition. An additive such as anoptically active compound, an antioxidant, an ultraviolet lightabsorber, a dye, an antifoaming agent, the polymerizable compound, apolymerization initiator and a polymerization inhibitor is added to thecomposition when necessary. A ratio (content) of the additive isexpressed in terms of weight percent (% by weight) based on the weightof the liquid crystal composition in a manner similar to the ratio ofthe liquid crystal compound. Weight parts per million (ppm) may beoccasionally used. A ratio of the polymerization initiator and thepolymerization inhibitor is exceptionally expressed based on the weightof the polymerizable compound.

An expression “maximum temperature range of the nematic phase” may beoccasionally abbreviated as “maximum temperature.” An expression“minimum temperature range of the nematic phase” may be occasionallyabbreviated as “minimum temperature.” An expression “having a largespecific resistance” means that the composition has a large specificresistance at room temperature and also at a temperature close to themaximum temperature of the nematic phase in an initial stage, and thecomposition has the large specific resistance at room temperature andalso at a temperature close to the maximum temperature of the nematicphase even after the device has been used for a long period of time. Anexpression “having a large voltage holding ratio” means that the devicehas a large voltage holding ratio at room temperature and also at atemperature close to the maximum temperature of the nematic phase in theinitial stage, and the device has the large voltage holding ratio atroom temperature and also at a temperature close to the maximumtemperature of the nematic phase even after the device has been used forthe long period of time. An expression “increase the dielectricanisotropy” means that a value of dielectric anisotropy positivelyincreases in a liquid crystal composition having a positive dielectricanisotropy, and the value of dielectric anisotropy negatively increasesin a liquid crystal composition having a negative dielectric anisotropy.

An expression “at least one of ‘A’ may be replaced by ‘B’” means thatthe number of ‘A’ is arbitrary. A position of ‘A’ is arbitrary when thenumber of ‘A’ is 1, and also positions thereof can be selected withoutrestriction when the number of ‘A’ is 2 or more. A same rule alsoapplies to an expression “at least one of ‘A’ is replaced by ‘B’.”

A symbol of terminal group R⁴ is used for a plurality of compounds inchemical formulas of component compounds. In the compounds, two groupsrepresented by two of arbitrary R⁴ may be identical or different. In onecase, for example, R⁴ of compound (2-1) is ethyl and R⁴ of compound(2-2) is ethyl. In another case, for example, R⁴ of compound (2-1) isethyl and R⁴ of compound (2-2) is propyl. A same rule also applies toany other symbol of a terminal group or the like. In formula (2), when ais 2, two of ring A exists. In the compound, two rings represented bytwo of ring A may be identical or different. A same rule applies to twoof arbitrary ring A when a is larger than 2. A same rule also applies toa symbol of Z⁴ and a ring D or the like.

Then, 2-fluoro-1,4-phenylene means two divalent groups described below.In a chemical formula, fluorine may be leftward (L) or rightward (R). Asame rule applies also to a divalent group of asymmetrical ring such astetrahydropyran-2,5-diyl.

The invention includes the items described below.

Item 1. A liquid crystal composition that has a negative dielectricanisotropy and a nematic phase, and contains at least one compoundselected from the group of compounds represented by formula (1) as anadditive, and at least one compound selected from the group of compoundsrepresented by formula (2) as a first component:

wherein, in formula (1) and formula (2), R¹ and R² are independentlyhydrogen or alkyl having 1 to 15 carbons; R³ and R⁴ are independentlyalkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons, alkenylhaving 2 to 12 carbons or alkenyloxy having 2 to 12 carbons; ring A andring C are independently 1,4-cyclohexylene, 1,4-cyclohexenylene,1,4-phenylene, 1,4-phenylene in which at least one of hydrogen isreplaced by fluorine or chlorine, or tetrahydropyran-2,5-diyl; ring B is2,3-difluoro-1,4-phenylene, 2-chloro-3-fluoro-1,4-phenylene,2,3-difluoro-5-methyl-1,4-phenylene, 3,4,5-trifluoronaphthalene-2,6-diylor 7,8-difluorochroman-2,6-diyl; Z¹ is alkylene having 1 to 20 carbons,and in the alkylene, at least one of hydrogen may be replaced byhalogen, and at least one of —CH₂— may be replaced by —O—; Z² and Z³ areindependently a single bond, ethylene, methyleneoxy or carbonyloxy, andwhen all of Z² are a single bond, R³ is alkenyl having 2 to 12 carbonsor alkenyloxy having 2 to 12 carbons; and a is 1, 2 or 3, b is 0 or 1,and a sum of a and b is 3 or less.

Item 2. The liquid crystal composition according to item 1, wherein aratio of the compound represented by formula (1) is in the range of0.005% by weight to 1% by weight based on the weight of the liquidcrystal composition.

Item 3. The liquid crystal composition according to item 1 or 2,containing at least one compound selected from the group of compoundsrepresented by formulas (2-1) to (2-12) as the first component:

wherein, in formula (2-1) to formula (2-12), R⁴ and R⁵ are independentlyalkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons, alkenylhaving 2 to 12 carbons or alkenyloxy having 2 to 12 carbons; and R⁶ isalkenyl having 2 to 12 carbons or alkenyloxy having 2 to 12 carbons.

Item 4. The liquid crystal composition according to any one of items 1to 3, wherein a ratio of the first component is in the range of 10% byweight to 90% by weight based on the weight of the liquid crystalcomposition.

Item 5. The liquid crystal composition according to any one of items 1to 4, containing at least one compound selected from the group ofcompounds represented by formula (3) as a second component:

wherein, in formula (3), R⁷ and R⁸ are independently alkyl having 1 to12 carbons, alkoxy having 1 to 12 carbons, alkenyl having 2 to 12carbons, or alkenyl having 2 to 12 carbons in which at least one ofhydrogen is replaced by fluorine; ring D and ring E are independently1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene or2,5-difluoro-1,4-phenylene; Z⁴ is a single bond, ethylene orcarbonyloxy; and c is 1, 2 or 3.

Item 6. The liquid crystal composition according to any one of items 1to 5, containing at least one compound selected from the group ofcompounds represented by formulas (3-1) to (3-13) as the secondcomponent:

wherein, in formula (3-1) to formula (3-13), R⁷ and R⁸ are independentlyalkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons, alkenylhaving 2 to 12 carbons, or alkenyl having 2 to 12 carbons in which atleast one of hydrogen is replaced by fluorine.

Item 7. The liquid crystal composition according to item 5 or 6, whereina ratio of the second component is in the range of 10% by weight to 90%by weight based on the weight of the liquid crystal composition.

Item 8. The liquid crystal composition according to any one of items 1to 7, containing at least one compound selected from the group ofcompounds represented by formula (4) as a third component:

wherein, in formula (4), R⁹ and R¹⁰ are independently alkyl having 1 to12 carbons or alkoxy having 1 to 12 carbons; ring F and ring I areindependently 1,4-cyclohexylene, 1,4-cyclohexenylene, 1,4-phenylene,1,4-phenylene in which at least one of hydrogen is replaced by fluorineor chlorine, or tetrahydropyran-2,5-diyl; ring G is2,3-difluoro-1,4-phenylene, 2-chloro-3-fluoro-1,4-phenylene,2,3-difluoro-5-methyl-1,4-phenylene, 3,4,5-trifluoronaphthalene-2,6-diylor 7,8-difluorochroman-2,6-diyl; and d is 1, 2 or 3, e is 0 or 1, and asum of d and e is 3 or less.

Item 9. The liquid crystal composition according to any one of items 1to 8, containing at least one compound selected from the group ofcompounds represented by formulas (4-1) to (4-11) as the thirdcomponent:

wherein, in formula (4-1) to formula (4-11), R⁹ and R¹⁰ areindependently alkyl having 1 to 12 carbons or alkoxy having 1 to 12carbons.

Item 10. The liquid crystal composition according to item 8 or 9,wherein a ratio of the third component is in the range of 5% by weightto 70% by weight based on the weight of the liquid crystal composition.

Item 11. The liquid crystal composition according to any one of items 1to 10, wherein a maximum temperature of a nematic phase is 70° C. orhigher, an optical anisotropy (measured at 25° C.) at a wavelength of589 nanometers is 0.08 or more and a dielectric anisotropy (measured at25° C.) at a frequency of 1 kHz is less than −2.

Item 12. A liquid crystal display device, including the liquid crystalcomposition according to any one of items 1 to 11.

Item 13. The liquid crystal display device according to item 12, whereinan operating mode in the liquid crystal display device includes an IPSmode, a VA mode, a PSA mode, an FFS mode or an FPA mode, and a drivingmode in the liquid crystal display device includes an active matrixmode.

Item 14. Use of the liquid crystal composition according to any one ofitems 1 to 11 in a liquid crystal display device.

The invention further includes the following items: (a) the composition,further containing at least one of additives such as an optically activecompound, an antioxidant, an ultraviolet light absorber, a dye, anantifoaming agent, a polymerizable compound, a polymerization initiatoror a polymerization inhibitor; (b) an AM device including thecomposition; (c) the composition further containing the polymerizablecompound, and a polymer sustained alignment (PSA) mode AM deviceincluding the composition; (d) a polymer sustained alignment (PSA) modeAM device, wherein the device including the composition, and apolymerizable compound in the composition is polymerized; (e) a deviceincluding the composition and having the PC mode, the TN mode, the STNmode, the ECB mode, the OCB mode, the IPS mode, the VA mode, the FFSmode or the FPA mode; (f) a transmissive device including thecomposition; (g) use of the composition as the composition having thenematic phase; (h) use as an optically active composition by adding theoptically active compound to the composition.

The composition of the invention will be described in the followingorder. First, a constitution of the component compounds in thecomposition will be described. Second, main characteristics of thecomponent compounds and main effects of the compounds on the compositionwill be described. Third, a combination of components in thecomposition, a preferred ratio of the components and the basis thereofwill be described. Fourth, a preferred embodiment of the componentcompounds will be described. Fifth, a preferred component compound willbe shown. Sixth, an additive that may be added to the composition willbe described. Seventh, methods for synthesizing the component compoundswill be described. Last, an application of the composition will bedescribed.

First, the constitution of the component compounds in the compositionwill be described. The composition of the invention is classified intocomposition A and composition B. Composition A may further contain anyother liquid crystal compound, additive or the like in addition to thecompound selected from compound (1), compound (2), compound (3) andcompound (4). An expression “any other liquid crystal compound” means aliquid crystal compound different from compound (2), compound (3) andcompound (4). Such a compound is mixed with the composition for thepurpose of further adjusting the characteristics. The additive is theoptically active compound, the antioxidant, the ultraviolet lightabsorber, the dye, the antifoaming agent, the polymerizable compound,the polymerization initiator, the polymerization inhibitor or the like.

Composition B consists essentially of liquid crystal compounds selectedfrom compound (1), compound (2), compound (3) and compound (4). Anexpression “essentially” means that the composition may contain theadditive, but contains no other liquid crystal compounds. Composition Bhas a smaller number of components than composition A has. Composition Bis preferred to composition A in view of cost reduction. Composition Ais preferred to composition B in view of possibility of furtheradjusting the characteristics by mixing any other liquid crystalcompound.

Second, the main characteristics of the component compounds and the maineffects of the compounds on the composition will be described. The maincharacteristics of the component compounds are summarized in Table 2 onthe basis of advantageous effects of the invention. In Table 2, a symbolL stands for “large” or “high,” a symbol M stands for “medium” and asymbol S stands for “small” or “low.” The symbols L, M and S represent aclassification based on a qualitative comparison among the componentcompounds, and 0 (zero) means “a value is nearly zero.”

TABLE 2 Characteristics of Compounds Compounds Compound (2) Compound (3)Compound (4) Maximum temperature S to M S to L S to M Viscosity L S to ML Optical anisotropy M to L S to L M to L Dielectric anisotropy L¹⁾ 0L¹⁾ Specific resistance L L L ¹⁾A value of dielectric anisotropy isnegative, and the symbol shows magnitude of an absolute value

Upon mixing the component compounds with the composition, the maineffects of the component compounds on the characteristics of thecomposition are as described below. Compound (1) contributes to a highstability to heat or ultraviolet light. Compound (1) gives no differencefor the characteristics such as a maximum temperature, opticalanisotropy and dielectric anisotropy. Compound (2) as the firstcomponent increases the dielectric anisotropy and decreases a minimumtemperature. Compound (3) as the second component decreases theviscosity or increases the maximum temperature. Compound (4) as thethird component increases the dielectric anisotropy and increasesstability.

Third, the combination of components in the composition, the preferredratio of the component compounds and the basis thereof will bedescribed. A preferred combination of components in the compositionincludes a combination of compound (1) and the first component, acombination of compound (1) and the first component and the secondcomponent, a combination of compound (1) and the first component and thethird component, or a combination of compound (1) and the firstcomponent and the second component and the third component. A furtherpreferred combination includes a combination of compound (1) and thefirst component and the second component and the third component.

A preferred ratio of compound (1) is about 0.005% by weight or more inorder to contribute to a high stability to heat or ultraviolet light,and about 1% by weight or less in order to decrease a minimumtemperature. A further preferred ratio is in the range of about 0.01% byweight to about 0.5% by weight. A particularly preferred ratio is in therange of about 0.03% by weight to about 0.3% by weight.

A preferred ratio of the first component is about 10% by weight or morefor increasing the dielectric anisotropy, and about 90% by weight orless for decreasing the minimum temperature. A further preferred ratiois in the range of about 15% by weight to about 80% by weight. Aparticularly preferred ratio is in the range of about 20% by weight toabout 70% by weight.

A preferred ratio of the second component is about 10% by weight or morefor increasing the maximum temperature or for decreasing the viscosity,and about 90% by weight or less for increasing the dielectricanisotropy. A further preferred ratio is in the range of about 20% byweight to about 80% by weight. A particularly preferred ratio is in therange of about 30% by weight to about 70% by weight.

A preferred ratio of the third component is about 5% by weight or morefor increasing the dielectric anisotropy, and about 70% by weight orless for decreasing the minimum temperature. A further preferred ratiois in the range of about 5% by weight to about 60% by weight. Aparticularly preferred ratio is in the range of about 10% by weight toabout 50% by weight.

Fourth, the preferred embodiment of the component compounds will bedescribed. In formula (1), R¹ and R² are independently hydrogen or alkylhaving 1 to 15 carbons.

Z¹ is alkylene having 1 to 20 carbons, and in the alkylene, at least oneof hydrogen may be replaced by halogen, and at least one of —CH₂— may bereplaced by —O—. Preferred Z¹ is alkylene having 1 to 20 carbons inwhich one or two of —CH₂— may be replaced by —O—. Further preferred Z¹is alkylene having 4 to 16 carbons. Preferred halogen is fluorine orchlorine.

In formulas (2), formula (3) and formula (4), R³ and R⁴ areindependently alkyl having 1 to 12 carbons, alkoxy having 1 to 12carbons, alkenyl having 2 to 12 carbons or alkenyloxy having 2 to 12carbons, and when all of Z² are a single bond, R³ is alkenyl having 2 to12 carbons or alkenyloxy having 2 to 12 carbons. Preferred R³ or R⁴ isalkyl having 1 to 12 carbons for increasing the stability, and alkoxyhaving 1 to 12 carbons for increasing the dielectric anisotropy, andalkenyl having 2 to 12 carbons for decreasing the viscosity. R⁵ is alkylhaving 1 to 12 carbons, alkoxy having 1 to 12 carbons, alkenyl having 2to 12 carbons or alkenyloxy having 2 to 12 carbons. Preferred R⁵ isalkyl having 1 to 12 carbons for increasing the stability. R⁶ is alkenylhaving 2 to 12 carbons or alkenyloxy having 2 to 12 carbons. PreferredR⁶ is alkenyl having 2 to 12 carbons for decreasing the viscosity. R⁷and R⁸ are independently alkyl having 1 to 12 carbons, alkoxy having 1to 12 carbons, alkenyl having 2 to 12 carbons, or alkenyl having 2 to 12carbons in which at least one of hydrogen is replaced by fluorine.Preferred R⁷ or R⁸ is alkenyl having 2 to 12 carbons for decreasing theviscosity, and alkyl having 1 to 12 carbons for increasing thestability. R⁹ and R¹⁰ are independently alkyl having 1 to 12 carbons oralkoxy having 1 to 12 carbons. Preferred R⁹ or R¹⁰ is alkyl having 1 to12 carbons for increasing the stability, and alkoxy having 1 to 12carbons for increasing the dielectric anisotropy.

Preferred alkyl is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptylor octyl. Further preferred alkyl is ethyl, propyl, butyl, pentyl orheptyl for decreasing the viscosity.

Preferred alkoxy is methoxy, ethoxy, propoxy, butoxy, pentyloxy,hexyloxy or heptyloxy. Further preferred alkoxy is methoxy or ethoxy fordecreasing the viscosity.

Preferred alkenyl is vinyl, 1-propenyl, 2-propenyl, 1-butenyl,2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl,1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl or 5-hexenyl. Furtherpreferred alkenyl is vinyl, 1-propenyl, 3-butenyl or 3-pentenyl fordecreasing the viscosity. A preferred configuration of —CH═CH— in thealkenyl depends on a position of a double bond. Trans is preferred inalkenyl such as 1-propenyl, 1-butenyl, 1-pentenyl, 1-hexenyl, 3-pentenyland 3-hexenyl for decreasing the viscosity or the like. Cis is preferredin alkenyl such as 2-butenyl, 2-pentenyl and 2-hexenyl. In the alkenyl,straight-chain alkenyl is preferred to branched-chain alkenyl.

Preferred alkenyloxy is vinyloxy, allyloxy, 3-butenyloxy, 3-pentenyloxyor 4-pentenyloxy. Further preferred alkenyloxy is allyloxy or3-butenyloxy for decreasing the viscosity.

Preferred examples of alkenyl in which at least one of hydrogen isreplaced by fluorine include 2,2-difluorovinyl, 3,3-difluoro-2-propenyl,4,4-difluoro-3-butenyl, 5,5-difluoro-4-pentenyl or6,6-difluoro-5-hexenyl. Further preferred examples include2,2-difluorovinyl or 4,4-difluoro-3-butenyl for decreasing theviscosity.

Ring A or ring C is independently 1,4-cyclohexylene,1,4-cyclohexenylene, 1,4-phenylene, 1,4-phenylene in which at least oneof hydrogen is replaced by fluorine or chlorine, ortetrahydropyran-2,5-diyl. Preferred examples of 1,4-phenylene in whichat least one of hydrogen is replaced by fluorine or chlorine include2-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene or2-chloro-3-fluoro-1,4-phenylene. Preferred ring A or ring C is1,4-cyclohexylene for decreasing the viscosity, tetrahydropyran-2,5-diylfor increasing the dielectric anisotropy, and 1,4-phenylene forincreasing the optical anisotropy. With regard to the configuration of1,4-cyclohexylene, trans is preferred to cis for increasing the maximumtemperature. Tetrahydropyran-2,5-diyl includes:

preferably

Ring B is 2,3-difluoro-1,4-phenylene, 2-chloro-3-fluoro-1,4-phenylene,2,3-difluoro-5-methyl-1,4-phenylene, 3,4,5-trifluoronaphthalene-2,6-diylor 7,8-difluorochroman-2,6-diyl. Preferred ring B is2,3-difluoro-1,4-phenylene for decreasing the viscosity, and7,8-difluorochroman-2,6-diyl for increasing the dielectric anisotropy.

Ring D and ring E are independently 1,4-cyclohexylene, 1,4-phenylene,2-fluoro-1,4-phenylene or 2,5-difluoro-1,4-phenylene. Preferred ring Dor ring E is 1,4-cyclohexylene for decreasing the viscosity or forincreasing the maximum temperature, and 1,4-phenylene for decreasing theminimum temperature.

Ring F and ring I are independently 1,4-cyclohexylene,1,4-cyclohexenylene, 1,4-phenylene, 1,4-phenylene in which at least oneof hydrogen is replaced by fluorine or chlorine, ortetrahydropyran-2,5-diyl. Preferred ring F or ring I is1,4-cyclohexylene for decreasing the viscosity, tetrahydropyran-2,5-diylfor increasing the dielectric anisotropy, and 1,4-phenylene forincreasing the optical anisotropy.

Ring G is 2,3-difluoro-1,4-phenylene, 2-chloro-3-fluoro-1,4-phenylene,2,3-difluoro-5-methyl-1,4-phenylene, 3,4,5-trifluoronaphthalene-2,6-diylor 7,8-difluorochroman-2,6-diyl. Preferred ring G is2,3-difluoro-1,4-phenylene for decreasing the viscosity, and2-chloro-3-fluoro-1,4-phenylene for decreasing the optical anisotropy.

Z² and Z³ are independently a single bond, ethylene, methyleneoxy orcarbonyloxy. Preferred Z² or Z³ is a single bond for decreasing theviscosity, ethylene for decreasing the minimum temperature, andmethyleneoxy for increasing the dielectric anisotropy. Z⁴ is a singlebond, ethylene or carbonyloxy. Preferred Z⁴ is a single bond fordecreasing the viscosity.

Then, a is 1, 2 or 3. Preferred a is 1 for decreasing the viscosity, and2 or 3 for increasing the maximum temperature. Then, b is 0 or 1.Preferred b is 0 for decreasing the viscosity, and 1 for decreasing theminimum temperature. Then, c is 1, 2 or 3. Preferred c is 1 fordecreasing the viscosity, and 2 or 3 for increasing the maximumtemperature. Then, d is 1, 2 or 3. Preferred d is 1 for decreasing theviscosity, and 2 or 3 for increasing the maximum temperature. Then, e is0 or 1. Preferred e is 0 for decreasing the viscosity, and 1 fordecreasing the minimum temperature.

Fifth, the preferred component compounds will be shown. Preferredcompound (1) includes compound (1-1) described below.

In compound (1-1), m is an integer from 1 to 20. Further preferredcompound (1) is a compound (1-1) wherein m is 8.

Preferred compound (2) includes compound (2-1) to compound (2-12)described above. In the compounds, at least one of the first componentpreferably includes compound (2-1), compound (2-2), compound (2-3),compound (2-4), compound (2-5), compound (2-7) or compound (2-9). Atleast two of the first component preferably includes a combination ofcompound (2-1) and compound (2-5), a combination of compound (2-1) andcompound (2-9), a combination of compound (2-3) and compound (2-5), acombination of compound (2-3) and compound (2-9) or a combination ofcompound (2-4) and compound (2-7).

Preferred compound (3) includes compound (3-1) to compound (3-13)described above. In the compounds, at least one of the second componentpreferably includes compound (3-1), compound (3-3), compound (3-5),compound (3-6), compound (3-7) or compound (3-8). At least two of thesecond component preferably includes a combination of compound (3-1) andcompound (3-3), a combination of compound (3-1) and compound (3-5) or acombination of compound (3-1) and compound (3-6).

Preferred compound (4) includes compound (4-1) to compound (4-11)described above. In the compounds, at least one of the first componentpreferably includes compound (4-1), compound (4-2), compound (4-4) orcompound (4-8). At least two of the first component preferably includesa combination of compound (4-1) and compound (4-4), a combination ofcompound (4-1) and compound (4-8) or a combination of compound (4-2) andcompound (4-8).

Sixth, the additive that may be added to the composition will bedescribed. Such an additive includes the optically active compound, theantioxidant, the ultraviolet light absorber, the dye, the antifoamingagent, the polymerizable compound, the polymerization initiator, thepolymerization inhibitor or the like. The optically active compound isadded to the composition for inducing a helical structure in a liquidcrystal to give a twist angle. Examples of such a compound includecompound (5-1) to compound (5-5). A preferred ratio of the opticallyactive compound is about 5% by weight or less. A further preferred ratiois in the range of about 0.01% by weight to about 2% by weight.

The antioxidant is added to the composition for preventing a decrease inthe specific resistance caused by heating in air, or for maintaining alarge voltage holding ratio at room temperature and also at thetemperature close to the maximum temperature after the device has beenused for a long period of time. Preferred examples of the antioxidantinclude compound (6) where n is an integer from 1 to 9 or the like.

In compound (6), preferred n is 1, 3, 5, 7 or 9. Further preferred n is1 or 7: Compound (6) where n is 1 is effective for preventing thedecrease in the specific resistance caused by heating in air because thecompound (6) has a large volatility. Compound (6) where n is 7 iseffective for maintaining the large voltage holding ratio at roomtemperature and also at the temperature close to the maximum temperatureeven after the device has been used for a long period of time becausethe compound (6) has a small volatility. A preferred ratio of theantioxidant is about 50 ppm or more for achieving an effect thereof, andabout 600 ppm or less for avoiding a decrease in the maximum temperatureor an increase in the minimum temperature. A further preferred ratio isin the range of about 100 ppm to about 300 ppm.

Preferred examples of the ultraviolet light absorber include abenzophenone derivative, a benzoate derivative and a triazolederivative. A light stabilizer such as an amine having steric hindranceis also preferred. A preferred ratio of the absorber or the stabilizeris about 50 ppm or more for achieving an effect thereof, and about10,000 ppm or less for avoiding the decrease in the maximum temperatureor avoiding the increase in the minimum temperature. A further preferredratio is in the range of about 100 ppm to about 10,000 ppm.

A dichroic dye such as an azo dye or an anthraquinone dye is added tothe composition for the purpose of adapting the composition to a devicehaving a guest host (GH) mode. A preferred ratio of the dye is in therange of about 0.01% by weight to about 10% by weight. The antifoamingagent such as dimethyl silicone oil or methyl phenyl silicone oil isadded to the composition for preventing foam formation. A preferredratio of the antifoaming agent is about 1 ppm or more for achieving aneffect thereof, and about 1,000 ppm or less for avoiding a poor display.A further preferred ratio is in the range of about 1 ppm to about 500ppm.

The polymerizable compound is added to the composition for the purposeof adapting the composition to a device having the polymer sustainedalignment (PSA) mode. Preferred examples of polymerizable compoundsinclude a compound such as acrylate, methacrylate, a vinyl compound, avinyloxy compound, propenyl ether, an epoxy compound (oxirane, oxetane)and vinyl ketone. Examples of such a compound include compound (7-1) tocompound (7-9). Further preferred examples include an acrylatederivative or a methacrylate derivative. A preferred ratio of thepolymerizable compound is about 0.05% by weight or more for achieving aneffect thereof, and about 10% or less for avoiding a poor display. Afurther preferred ratio is in the range of about 0.1% by weight to about2% by weight.

In formula (7-1) to formula (7-9), R¹¹, R¹², R¹³ and R¹⁴ areindependently acryloyloxy (—OCO—CH═CH₂) or methacryloiloxy(—OCO—C(CH₃)═CH₂), and R¹⁵ and R¹⁶ are independently hydrogen, halogenor alkyl having 1 to 10 carbons; Z⁵, Z⁶, Z⁷ and Z⁸ are independently asingle bond or alkylene having 1 to 12 carbons, and in the alkylene, atleast one of —CH₂— may be replaced by —O— or —CH═CH—; f, g and h areindependently 0, 1 or 2. Preferred halogen is fluorine or chlorine. Incompound (7-1), a perpendicular line crossing a hexagonal shape meansthat arbitrary hydrogen on a six-membered ring may be replaced byfluorine. A subscript such as d represents the number of fluorine to bereplaced. A same rule applies also to compound (7-2) or the like. Incompound (7-1), a sum of f and g is 1 or more, and in compound (7-4), asum of f, g and h is 1 or more.

The polymerizable compound is polymerized by irradiation withultraviolet light. The polymerizable compound may be polymerized in thepresence of an initiator such as a photopolymerization initiator.Suitable conditions for polymerization, suitable types of the initiatorand suitable amounts thereof are known to those skilled in the art andare described in literature. For example, Irgacure 651 (registeredtrademark; BASF), Irgacure 184 (registered trademark; BASF) or Darocure1173 (registered trademark; BASF), each being a photoinitiator, issuitable for radical polymerization. A preferred ratio of thephotopolymerization initiator is in the range of about 0.1% by weight toabout 5% by weight based on the total weight of the polymerizablecompound. A further preferred ratio is in the range of about 1% byweight to about 3% by weight based thereon.

Upon storing the polymerizable compound, the polymerization inhibitormay be added thereto for preventing polymerization. The polymerizablecompound is ordinarily added to the composition without removing thepolymerization inhibitor. Examples of the polymerization inhibitorinclude hydroquinone and a hydroquinone derivative such asmethylhydroquinone, 4-tert-butylcatechol, 4-methoxyphenol orphenothiazine.

Seventh, the methods for synthesizing the component compounds will bedescribed. The compounds are synthesized by a known method. Examples ofthe synthetic methods are described. Compound (1-1) where m is 8 iscommercially available. Compound (2-1) is prepared by a method describedin JP 2000-053602 A. Compound (3-1) is prepared by a method described inJP S59-176221 A. Compound (3-13) is prepared by a method described in JPH2-237949 A. Compound (4-1) is prepared by a method described in JPS57-114532 A. A compound where n in formula (6) is 1 can be obtainedfrom Sigma-Aldrich Corporation. A compound where n in compound (6) is 7or the like can be prepared according to a method described in U.S. Pat.No. 3,660,505 B.

Any compounds whose synthetic methods are not described can be preparedaccording to methods described in books such as Organic Syntheses (JohnWiley & Sons, Inc.), Organic Reactions (John Wiley & Sons, Inc.),Comprehensive Organic Synthesis (Pergamon Press) and New ExperimentalChemistry Course (Shin Jikken Kagaku Koza in Japanese) (Maruzen Co.,Ltd.). The composition is prepared according to publicly known methodsusing the thus obtained compounds. For example, the component compoundsare mixed and dissolved in each other by heating.

Last, the application of the composition will be described. Thecomposition of the invention mainly has a minimum temperature of about−10° C. or lower, a maximum temperature of about 70° C. or higher, andan optical anisotropy in the range of about 0.07 to about 0.20. A deviceincluding the composition has the large voltage holding ratio. Thecomposition is suitable for use in the AM device. The composition isparticularly suitable for use in a transmissive AM device. Thecomposition having an optical anisotropy in the range of about 0.08 toabout 0.25 may be prepared by controlling the ratio of the componentcompounds or by mixing any other liquid crystal compound, and furtherthe composition having an optical anisotropy in the range of about 0.10to about 0.30 may be prepared. The composition can be used as thecomposition having the nematic phase, and as the optically activecomposition by adding the optically active compound.

The composition can be used for the AM device. The composition can alsobe used for a PM device. The composition can also be used for the AMdevice and the PM device each having a mode such as a PC mode, the TNmode, a STN mode, the ECB mode, the OCB mode, the IPS mode, the FFSmode, the VA mode and the FPA mode. Use for the AM device having the TNmode, the OCB mode, the IPS mode or the FFS mode is particularlypreferred. In the AM device having the IPS mode or the FFS mode,alignment of liquid crystal molecules when no voltage is applied may beparallel or vertical to a glass substrate. The device may be of areflective type, a transmissive type or a transflective type. Use forthe transmissive device is preferred. Use for an amorphous silicon-TFTdevice or a polycrystal silicon-TFT device is allowed. The compositioncan also be used for a nematic curvilinear aligned phase (NCAP) deviceprepared by microencapsulating the composition, or for a polymerdispersed (PD) device in which a three-dimensional network-polymer isformed in the composition.

EXAMPLES

The invention will be described in greater detail by way of Examples.However, the invention is not limited by the Examples. The inventionincludes a mixture of a composition in Example 1 and a composition inExample 2. The invention also includes a mixture in which at least twocompositions in Examples are mixed. The thus prepared compound wasidentified by methods such as an NMR analysis. Characteristics of thecompound and the composition were measured by methods described below.

NMR analysis: For measurement, DRX-500 made by Bruker BioSpinCorporation was used. In ¹H-NMR measurement, a sample was dissolved in adeuterated solvent such as CDCl₃, and measurement was carried out underconditions of room temperature, 500 MHZ and 16 times of accumulation.Tetramethylsilane (TMS) was used as an internal standard. In ¹⁹F-NMRmeasurement, CFCl₃ was used as an internal standard, and measurement wascarried out under conditions of 24 times of accumulation. In explainingnuclear magnetic resonance spectra obtained, s, d, t, q, quin, sex, mand r stand for a singlet, a doublet, a triplet, a quartet, a quintet, asextet and a multiplet, and br being broad, respectively.

Gas chromatographic analysis: GC-14B Gas Chromatograph made by ShimadzuCorporation was used for measurement. A carrier gas was helium (2 mL/perminute). A sample injector and a detector (FID) were set to 280° C. and300° C., respectively. A capillary column DB-1 (length 30 m, bore 0.32mm, film thickness 0.25 μm; dimethylpolysiloxane as a stationary phase,non-polar) made by Agilent Technologies, Inc. was used for separation ofcomponent compounds. After the column was kept at 200° C. for 2 minutes,the column was heated to 280° C. at a rate of 5° C. per minute. A samplewas prepared in an acetone solution (0.1% by weight), and then 1microliter of the solution was injected into the sample injector. Arecorder was C-R5A Chromatopac made by Shimadzu Corporation or theequivalent thereof. The resulting gas chromatogram showed a retentiontime of a peak and a peak area corresponding to each of the componentcompounds.

As a solvent for diluting the sample, chloroform, hexane or the like mayalso be used. The following capillary columns may also be used forseparating component compounds: HP-1 (length 30 m, bore 0.32 mm, filmthickness 0.25 μm) made by Agilent Technologies, Inc., Rtx-1 (length 30m, bore 0.32 mm, film thickness 0.25 μm) made by Restek Corporation andBP-1 (length 30 m, bore 0.32 mm, film thickness 0.25 μm) made by SGEInternational Pty. Ltd. A capillary column CBP1-M50-025 (length 50 m,bore 0.25 mm, film thickness 0.25 μm) made by Shimadzu Corporation mayalso be used for the purpose of avoiding an overlap of peaks of thecompounds.

A ratio of liquid crystal compounds contained in the composition may becalculated by the method as described below. The mixture of liquidcrystal compounds is detected by gas chromatograph (FID). An area ratioof each peak in the gas chromatogram corresponds to the ratio (weightratio) of the liquid crystal compound. When the capillary columnsdescribed above were used, a correction coefficient of each of theliquid crystal compounds may be regarded as 1 (one). Accordingly, theratio (% by weight) of the liquid crystal compound is calculated fromthe area ratio of each peak.

Sample for measurement: When characteristics of a composition wasmeasured, the composition was used as a sample as was. Upon measuringcharacteristics of a compound, a sample for measurement was prepared bymixing the compound (15% by weight) with a base liquid crystal (85% byweight). Values of characteristics of the compound were calculated,according to an extrapolation method, using values obtained bymeasurement. (Extrapolated value)={(measured value of a sample formeasurement)−0.85×(measured value of a base liquid crystal)}/0.15. Whena smectic phase (or crystals) precipitates at the ratio thereof at 25°C., a ratio of the compound to the base liquid crystal was changed stepby step in the order of (10% by weight:90% by weight), (5% by weight:95%by weight) and (1% by weight:99% by weight). Values of maximumtemperature, optical anisotropy, viscosity and dielectric anisotropywith regard to the compound were determined according to theextrapolation method.

A base liquid crystal described below was used. A ratio of the componentcompound was expressed in terms of weight percent (% by weight).

Measuring method: Measurement of characteristics was carried out by themethods described below. Most of the measuring methods are applied asdescribed in the Standard of the Japan Electronics and InformationTechnology Industries Association (hereinafter abbreviated as JEITA)(JEITA EIAJ ED-2521B) discussed and established by JEITA, or modifiedthereon. No thin film transistor (TFT) was attached to a TN device usedfor measurement.

(1) Maximum temperature of nematic phase (NI; ° C.): A sample was placedon a hot plate in a melting point apparatus equipped with a polarizingmicroscope, and heated at a rate of 1° C. per minute. Temperature whenpart of the sample began to change from a nematic phase to an isotropicliquid was measured. A higher limit of a temperature range of thenematic phase may be occasionally abbreviated as “Maximum temperature.”

(2) Minimum temperature of nematic phase (T_(c); ° C.): Samples eachhaving a nematic phase were put in glass vials and kept in freezers attemperatures of 0° C., −10° C., −20° C., −30° C. and −40° C. for 10days, and then liquid crystal phases were observed. For example, whenthe sample maintained the nematic phase at −20° C. and changed tocrystals or a smectic phase at −30° C., Tc of the sample was expressedas T_(c)<−20° C. A minimum temperature of the nematic phase may beoccasionally abbreviated as “minimum temperature.”

(3) Viscosity (bulk viscosity; q; measured at 20° C.; mPa·s): Acone-plate (E type) rotational viscometer made by Tokyo Keiki, Inc. wasused for measurement.

(4) Viscosity (rotational viscosity; γ1; measured at 25° C.; mPa·s):Measurement was carried out according to a method described in M. Imaiet al., Molecular Crystals and Liquid Crystals, Vol. 259, p. 37 (1995).A sample was put in a VA device in which a distance (cell gap) betweentwo glass substrates was 20 micrometers. Voltage was applied stepwise tothe device in the range of 39 V to 50 Vat an increment of 1 V. After aperiod of 0.2 second with no voltage application, voltage was appliedrepeatedly under the conditions of only one rectangular wave(rectangular pulse; 0.2 second) and no voltage application (2 seconds).A peak current and a peak time of a transient current generated by theapplied voltage were measured. A value of rotational viscosity wasobtained from the measured values and a calculation equation (8)described on page 40 of the paper presented by M. Imai et al. Dielectricanisotropy required for the calculation was measured according tosection (6) described below.

(5) Optical anisotropy (refractive index anisotropy; An; measured at 25°C.): Measurement was carried out by an Abbe refractometer with apolarizing plate mounted on an ocular, using light at a wavelength of589 nanometers. A surface of a main prism was rubbed in one direction,and then a sample was added dropwise onto the main prism. A refractiveindex (n∥) was measured when a direction of polarized light was parallelto a direction of rubbing. A refractive index (n⊥) was measured when thedirection of polarized light was perpendicular to the direction ofrubbing. A value of optical anisotropy was calculated from an equation:Δn=n∥−n⊥.

(6) Dielectric anisotropy (Δ∈; measured at 25° C.): A value ofdielectric anisotropy was calculated from an equation: Δ∈=∈∥−∈⊥. Adielectric constant (∈∥ and ∈⊥) was measured as described below.

1) Measurement of dielectric constant (∈∥): An ethanol (20 mL) solutionof octadecyl triethoxysilane (0.16 mL) was applied to a well-cleanedglass substrate. After rotating the glass substrate with a spinner, theglass substrate was heated at 150° C. for 1 hour. A sample was put in aVA device in which a distance (cell gap) between two glass substrateswas 4 micrometers, and the device was sealed with an ultraviolet-curableadhesive. Sine waves (0.5 V, 1 kHz) were applied to the device, andafter 2 seconds, a dielectric constant (∈∥) in a major axis direction ofliquid crystal molecules was measured.

2) Measurement of dielectric constant (∈⊥): A polyimide solution wasapplied to a well-cleaned glass substrate. After calcining the glasssubstrate, rubbing treatment was applied to the alignment film obtained.A sample was put in a TN device in which a distance (cell gap) betweentwo glass substrates was 9 micrometers and a twist angle was 80 degrees.Sine waves (0.5 V, 1 kHz) were applied to the device, and after 2seconds, a dielectric constant (SI) in a minor axis direction of theliquid crystal molecules was measured.

(7) Threshold voltage (Vth; measured at 25° C.; V): An LCD-5100luminance meter made by Otsuka Electronics Co., Ltd. was used formeasurement. A light source was a halogen lamp. A sample was put in anormally black mode VA device in which a distance (cell gap) between twoglass substrates was 4 micrometers and a rubbing direction wasanti-parallel, and the device was sealed with an ultraviolet-curableadhesive. A voltage (60 Hz, rectangular waves) to be applied to thedevice was stepwise increased from 0 V to 20 V at an increment of 0.02V. On the occasion, the device was irradiated with light from adirection perpendicular to the device, and an amount of lighttransmitted through the device was measured. A voltage-transmittancecurve was prepared, in which the maximum amount of light corresponds to100% transmittance and the minimum amount of light corresponds to 0%transmittance. A threshold voltage is expressed in terms of a voltage at10% transmittance.

(8) Voltage holding ratio (VHR-a; measured at 25° C.; %): A PVA deviceused for measurement had a polyimide alignment film, and a distance(cell gap) between two glass substrates was 3.5 micrometers. A samplewas put in the device, and the device was sealed with anultraviolet-curable adhesive. A pulse voltage (60 microseconds at 1 V)was applied to the PVA device and the device was charged. A decayingvoltage was measured for 166.7 milliseconds with a high-speed voltmeter,and area A between a voltage curve and a horizontal axis in a unit cyclewas determined. Area B is an area without decay. A voltage holding ratiois expressed in terms of a percentage of area A to area B.

(9) Voltage holding ratio (VHR-b; measured at 60° C.; %): A voltageholding ratio was measured according to procedures identical with theprocedures described above except that measurement was carried out at60° C. in place of 25° C. The thus obtained value was expressed in termsof VHR-b.

(10) Voltage holding ratio (VHR-c; measured at 60° C.; %): Stability toultraviolet light was evaluated by measuring a voltage holding ratioafter a device was irradiated with ultraviolet light. A PVA device usedfor measurement had a polyimide alignment film and a cell gap was 3.5micrometers. A sample was injected into the device, and then the devicewas irradiated with light for 167 minutes. A light source was blacklight (peak wavelength of 369 nm), and a distance between the device andthe light source was 5 millimeters. In measurement of VHR-c, a decayingvoltage was measured for 166.7 milliseconds. A composition having largeVHR-c has a large stability to ultraviolet light.

(11) Voltage holding ratio (VHR-d; measured at 60° C.; %): Stability toheat was evaluated by measuring a voltage holding ratio after a PVAdevice into which a sample was injected was heated in aconstant-temperature bath at 150° C. for 2 hours. In measurement ofVHR-d, a decaying voltage was measured for 166.7 milliseconds. Acomposition having large VHR-4 has a large stability to heat.

(12) Response Time (i; measured at 25° C.; ms): An LCD-5100 luminancemeter made by Otsuka Electronics Co., Ltd. was used for measurement. Alight source was a halogen lamp. A low-pass filter was set at 5 kHz. Asample was put in a normally black mode VA device in which a distance(cell gap) between two glass substrates was 4 micrometers and a rubbingdirection was anti-parallel. The device was sealed with anultraviolet-curable adhesive. A voltage (rectangular waves; 60 Hz, 10 V,0.5 second) was applied to the device. On the occasion, the device wasirradiated with light from a direction perpendicular to the device, andan amount of light transmitted through the device was measured: Avoltage-transmittance curve was prepared, in which the maximum amount oflight corresponds to 100% transmittance and the minimum amount of lightcorresponds to 0% transmittance. A response time was expressed in termsof time required for a change from 90% transmittance to 10%transmittance (fall time; millisecond).

(13) Specific resistance (ρ; measured at 25 C; Ωcm): Into a vesselequipped with electrodes, 1.0 mL of a sample was injected. A directcurrent voltage (10V) was applied to the vessel, and a direct currentafter 10 seconds was measured: Specific resistance was calculated fromthe following equation: (specific resistance)={(voltage)×(electriccapacity of the vessel)}/{(direct current)×(dielectric constant ofvacuum)}.

The compounds described in Examples were described using symbolsaccording to definitions in Table 3 below. In Table 3, the configurationof 1,4-cyclohexylene is trans. A parenthesized number next to asymbolized compound in Examples corresponds to the number of thecompound. A symbol (−) means any other liquid crystal compound. A ratio(percentage) of the liquid crystal compound is expressed in terms ofweight percent (% by weight) based on the weight of the liquid crystalcomposition. Values of the characteristics of the composition weresummarized in the last part.

TABLE 3 Method for Description of Compounds using SymbolsR—(A₁)—Z₁— - - - - - —Z_(n)—(A_(n))—R′ Symbol 1) Left-terminal Group R—C_(n)H_(2n+1)— n- C_(n)H_(2n+1)O— nO- C_(m)H_(2m+1)OC_(n)H_(2n)— mOn-CH₂═CH— V- C_(n)H_(2n+1)—CH═CH— nV- CH₂═CH—C_(n)H_(2n)— Vn-C_(m)H_(2m+1)—CH═CH—C_(n)H_(2n)— mVn- CF₂═CH— VFF- CF₂═CH—C_(n)H_(2n)—VFFn- CH₂═CH—COO— AC- CH₂═C(CH₃)—COO— MAC- 2) Right-terminal Group —R′—C_(n)H_(2n+1) -n —OC_(n)H_(2n+1) -On —CH═CH₂ -V —CH═CH—C_(n)H_(2n+1)-Vn —C_(n)H_(2n)—CH═CH₂ -nV —C_(m)H_(2m)—CH═CH—C_(n)H_(2n+1) -mVn—CH═CF₂ -VFF —OCO—CH═CH₂ -AC —OCO—C(CH₃)═CH₂ -MAC 3) Bonding Group—Z_(n)— —C_(n)H_(2n)— n —COO— E —CH═CH— V —CH═CHO— VO —OCH═CH— OV —CH₂O—1O —OCH₂— O1 4) Ring Structure —A_(n)—

H

B

B(F)

B(2F)

B(F,F)

B(2F,5F)

B(2F,3F)

B(2F,3CL)

B(2F,3F,6Me)

dh

Dh

oh

Cro(7F,8F) 5) Examples of Description Example 1. 2-BB(F)B-3

Example 2. 3-HHB(2F,3F)-O2

Example 3. V-HHB-1

Example 4. 3-HDhB(2F,3F)-O2

Example 1

2-H1OB(2F,3F)-O2 (2-3) 3% 3-H1OB(2F,3F)-O2 (2-3) 10% 1V2-BB(2F,3F)-O2(2-4) 10% V-HHB(2F,3F)-O1 (2-5) 10% V-HHB(2F,3F)-O2 (2-5) 10%3-HH1OB(2F,3F)-O2 (2-7) 6% 3-HH-V (3-1) 25% 3-HH-V1 (3-1) 6% 4-HH-V1(3-1) 3% V-HHB-1 (3-5) 3% V2-HHB-1 (3-5) 4% 3-HHB(2F,3F)-O2 (4-4) 4%2-BB(2F,3F)B-3 (4-5) 6%

A composition having negative dielectric anisotropy was prepared, andcharacteristics thereof were measured: NI=81.0° C.; T_(c)<−20° C.;Δn=0.103; Δ∈=−3.9; Vth=2.10 V; η=21.0 mPa·s.

To the composition, compound (1-1-1) was added at a ratio of 0.04% bythe weight, and VHR-c was measured. VHR-c=73.1%.

Comparative Example 1

VHR-c of the composition before adding compound (1-1-1) in Example 1 tothe composition was measured: VHR-c=35.9%.

Example 2

3-H1OB(2F,3F)-O2 (2-3) 7% V2-BB(2F,3F)-O1 (2-4) 4% V2-BB(2F,3F)-O2 (2-4)9% 1V2-BB(2F,3F)-O4 (2-4) 6% V-HHB(2F,3F)-O2 (2-5) 10% V-HHB(2F,3F)-O4(2-5) 3% 1V2-HHB(2F,3F)-O2 (2-5) 4% 3-HH1OB(2F,3F)-O2 (2-7) 12% 3-HH-V(3-1) 28% 1-HH-2V1 (3-1) 3% 3-HH-2V1 (3-1) 3% 5-HB-O2 (3-2) 3% 3-HHB-O1(3-5) 4% V-HHB-1 (3-5) 4%

The composition having negative dielectric anisotropy was prepared, andcharacteristics thereof were measured: NI=75.8° C.; T_(c)<−20° C.;Δn=0.098; Δ∈=−3.3; Vth=2.24 V; η=17.6 mPa·s.

To the composition, compound (1-1-1) was added at a ratio of 0.05% bythe weight, and VHR-c was measured. VHR-c=76.0%.

Example 3

3-H2B(2F,3F)-O2 (2-2) 15% 5-H2B(2F,3F)-O2 (2-2) 14% 2-HH-3 (3-1) 20%3-HH-4 (3-1) 8% V2-BB(F)B-1 (3-8) 4% 3-HHB(2F,3F)-O2 (4-4) 8%5-HHB(2F,3F)-O2 (4-4) 6% 2-HHB(2F,3F)-1 (4-4) 5% 3-HBB(2F,3F)-O2 (4-8)10% 4-HBB(2F,3F)-O2 (4-8) 6% 5-HBB(2F,3F)-O2 (4-8) 4%

The composition having negative dielectric anisotropy was prepared, andcharacteristics thereof were measured: NI=78.5° C.; T_(c)<−20° C.;Δn=0.095; Δ∈=−3.5; Vth=2.16 V; η=19.6 mPa·s.

To the composition, compound (1-2) was added at a ratio of 0.05% by theweight, and VHR-c was measured. VHR-c=88.9%.

Example 4

3-H1OB(2F,3F)-O2 (2-3) 9% 2-HH1OB(2F,3F)-O2 (2-7) 8% 3-HH1OB(2F,3F)-O2(2-7) 7% 3-HH-V (3-1) 24% 3-HH-V1 (3-1) 10% V2-HHB-1 (3-5) 9%3-BB(2F,3F)-O2 (4-2) 8% 2O-BB(2F,3F)-O2 (4-2) 5% 2-BB(2F,3F) B-3 (4-5)8% 3-HDhB(2F,3F)-O2 (4-7) 9% 1O1-HBBH-4 (—) 3%

The composition having negative dielectric anisotropy was prepared, andcharacteristics thereof were measured: NI=82.5° C.; T_(c)<−20° C.;Δn=0.107; Δ∈=−3.7; Vth=2.19 V; η=22.7 mPa·s.

To the composition, compound (1-1-1) was added at a ratio of 0.05% bythe weight, and VHR-c was measured. VHR-c=74.3%.

Example 5

V2-BB(2F,3F)-O2 (2-4) 12% 1V2-BB(2F,3F)-O2 (2-4) 4% 1V2-BB(2F,3F)-O4(2-4) 3% V-HHB(2F,3F)-O1 (2-5) 5% V-HHB(2F,3F)-O2 (2-5) 12%V-HHB(2F,3F)-O4 (2-5) 5% 3-HH-V (3-1) 31% 1-BB-3 (3-3) 6% 3-HHEH-3 (3-4)3% V-HHB-1 (3-5) 3% 1-BB(F)B-2V (3-8) 3% 3-HHEBH-4 (3-9) 3%3-HB(2F,3F)-O4 (4-1) 5% 3-HDhB(2F,3F)-O2 (4-7) 5%

The composition having negative dielectric anisotropy was prepared, andcharacteristics thereof were measured: NI=71.9° C.; T_(c)<−20° C.;Δn=0.102; Δ∈=−2.6; Vth=2.30 V; η=17.7 mPa·s.

To the composition, compound (1-1-1) was added at a ratio of 0.07% bythe weight, and VHR-c was measured. VHR-c=76.9%.

Example 6

V2-BB(2F,3F)-O2 (2-4) 12% 1V2-BB(2F,3F)-O2 (2-4) 6% V-HHB(2F,3F)-O1(2-5) 6% V-HHB(2F,3F)-O2 (2-5) 7% V-HHB(2F,3F)-O4 (2-5) 5%1V2-HHB(2F,3F)-O4 (2-5) 5% 3-DhH1OB(2F,3F)-O2 (2-8) 3% 3-HH-V (3-1) 26%3-HH-VFF (3-1) 3% V2-HB-1 (3-2) 6% V-HHB-1 (3-5) 5% 2-BB(F)B-5 (3-8) 3%5-HBB(F)B-3 (3-13) 3% 3-dhBB(2F,3F)-O2 (4-9) 6% 3-HHB(2F,3CL)-O2 (4-10)4%

The composition having negative dielectric anisotropy was prepared, andcharacteristics thereof were measured: NI=82.9° C.; T_(c)<−20° C.;Δn=0.111; Δ∈=−2.9; Vth=2.39 V; η=21.0 mPa·s.

To the composition, compound (1-1-1) was added at a ratio of 0.1% by theweight, and VHR-c was measured. VHR-c=79.8%.

Example 7

3-H1OB(2F,3F)-O2 (2-3) 10% 1V2-BB(2F,3F)-O2 (2-4) 10% V-HHB(2F,3F)-O1(2-5) 11% V-HHB(2F,3F)-O2 (2-5) 12% 3-HH1OB(2F,3F)-O2 (2-7) 9% 3-HH-V(3-1) 26% 3-HH-V1 (3-1) 6% 1-HH-2V1 (3-1) 3% 3-HHB-3 (3-5) 3%2-BB(2F,3F)B-3 (4-5) 7% 2-BB(2F,3F)B-4 (4-5) 3%

The composition having negative dielectric anisotropy was prepared, andcharacteristics thereof were measured: NI=80.5° C.; T_(c)<−20° C.;Δn=0.107; Δ∈=−3.8; Vth=2.11 V; η=21.6 mPa·s.

To the composition, compound (1-1-1) was added at a ratio of 0.06% bythe weight, and VHR-c was measured. VHR-c=73.6%.

Example 8

3-H1OB(2F,3F)-O2 (2-3) 8% 2-HH1OB(2F,3F)-O2 (2-7) 8% 3-HH1OB(2F,3F)-O2(2-7) 10% 1V2-HBB(2F,3F)-O2 (2-9) 6% 3-HH-V (3-1) 25% 3-HH-V1 (3-1) 10%V2-HHB-1 (3-5) 9% 2-BB(F)B-3 (3-8) 8% 3-HB(2F,3F)-O2 (4-1) 8%3-BB(2F,3F)-O2 (4-2) 5% 3-HDhB(2F,3F)-O2 (4-7) 3%

The composition having negative dielectric anisotropy was prepared, andcharacteristics thereof were measured: NI=82.4° C.; T_(c)<−20° C.;Δn=0.106; Δ∈=−3.6; Vth=2.21 V; η=19.1 mPa·s.

To the composition, compound (1-1-1) was added at a ratio of 0.05% bythe weight, and VHR-c was measured. VHR-c=76.0%.

Example 9

V-HB(2F,3F)-O2 (2-1) 4% V2-HB(2F,3F)-O2 (2-1) 5% 3-H2B(2F,3F)-O2 (2-2)9% 2-HH1OB(2F,3F)-O2 (2-7) 7% 3-HH1OB(2F,3F)-O2 (2-7) 12% 2-HH-3 (3-1)27% 1-BB-3 (3-3) 12% 3-HHB-1 (3-5) 3% 3-B(F)BB-2 (3-7) 3% 3-HB(F)HH-5(3-10) 3% 3-HB(F)BH-3 (3-12) 3% 3-HHB(2F,3F)-O2 (4-4) 12%

The composition having negative dielectric anisotropy was prepared, andcharacteristics thereof were measured: NI=74.7° C.; T_(c)<−20° C.;Δn=0.095; Δ∈=−2.9; Vth=2.31 V; η=17.3 mPa·s.

To the composition, compound (1-1-1) was added at a ratio of 0.03% bythe weight, and VHR-c was measured. VHR-c=78.5%.

Example 10

5-H2B(2F,3F)-O2 (2-2) 9% V-HHB(2F,3F)-O2 (2-5) 6% 3-HH2B(2F,3F)-O2 (2-6)3% 2-HH1OB(2F,3F)-O2 (2-7) 4% 3-HH1OB(2F,3F)-O2 (2-7) 9% 2-HH-3 (3-1)22% 3-HH-V (3-1) 4% V2-BB-1 (3-3) 4% 1-BB-3 (3-3) 13% 3-HB(F)HH-5 (3-10)3% 5-HBBH-3 (3-11) 3% 3-HB(F)BH-3 (3-12) 3% 5-BB(2F,3F)-O4 (4-2) 5%5-HHB(2F,3F)-O2 (4-4) 3% 2-BB(2F,3F)B-3 (4-5) 3% 2-HHB(2F,3CL)-O2 (4-10)3% 4-HHB(2F,3CL)-O2 (4-10) 3%

The composition having negative dielectric anisotropy was prepared, andcharacteristics thereof were measured: NI=77.8° C.; T_(c)<−20° C.;Δn=0.104; Δ∈=−2.6; Vth=2.47 V; ηmPa·s.

To the composition, compound (1-1-1) was added at a ratio of 0.05% bythe weight, and VHR-c was measured. VHR-c=79.1%.

Example 11

3-H2B(2F,3F)-O2 (2-2) 20% 5-H2B(2F,3F)-O2 (2-2) 12% 2-HH-3 (3-1) 16%3-HH-4 (3-1) 12% 1V-HBB-2 (3-6) 4% 3-HHB(2F,3F)-O2 (4-4) 9%5-HHB(2F,3F)-O2 (4-4) 6% 3-HDhB(2F,3F)-O2 (4-7) 5% 3-HBB(2F,3F)-O2 (4-8)11% 4-HBB(2F,3F)-O2 (4-8) 5%

The composition having negative dielectric anisotropy was prepared, andcharacteristics thereof were measured: NI=77.2° C.; T_(c)<−20° C.;Δn=0.090; Δ∈=−3.6; Vth=2.13 V; η=20.3 mPa·s.

To the composition, compound (1-1-1) was added at a ratio of 0.03% bythe weight, and VHR-c was measured. VHR-c=90.1%.

Example 12

V-HB(2F,3F)-O4 (2-1) 3% V-HHB(2F,3F)-O2 (2-5) 10% 3-HH1OB(2F,3F)-O2(2-7) 10% V-HBB(2F,3F)-O2 (2-9) 6% 3-HH-O1 (3-1) 3% 3-HH-V (3-1) 26%3-HB-O2 (3-2) 3% V-HHB-1 (3-5) 7% 3-BB(F)B-5 (3-8) 3% 3-HB(2F,3F)-O2(4-1) 5% 5-BB(2F,3F)-O2 (4-2) 6% 3-B(2F,3F)B(2F,3F)-O2 (4-3) 3%2-BB(2F,3F)B-3 (4-5) 5% 4-HBB(2F,3F)-O2 (4-8) 4% 3-HBB(2F,3CL)-O2 (4-11)3% 5-HBB(2F,3CL)-O2 (4-11) 3%

The composition having negative dielectric anisotropy was prepared, andcharacteristics thereof were measured: NI=82.3° C.; T_(c)<−20° C.;Δn=0.114; Δ∈=−3.2; Vth=2.29 V; η=25.2 mPa·s.

To the composition, compound (1-1-1) was added at a ratio of 0.1% by theweight, and VHR-c was measured. VHR-c=73.7%.

Example 13

V2-BB(2F,3F)-O2 (2-4) 12% V-HHB(2F,3F)-O1 (2-5) 6% V-HHB(2F,3F)-O2 (2-5)12% 3-HEB(2F,3F)B(2F,3F)-O2 (2-10) 3% 3-H1OCro(7F,8F)-5 (2-11) 3%3-HH1OCro(7F,8F)-5 (2-12) 3% 3-HH-V (3-1) 23% 4-HH-V (3-1) 3% 5-HH-V(3-1) 6% 7-HB-1 (3-2) 3% V-HHB-1 (3-5) 4% 3-HBB-2 (3-6) 5% 2-BB(F)B-3(3-8) 3% 3-BB(2F,3F)-O4 (4-2) 6% 3-HHB(2F,3F)-O2 (4-4) 5%3-DhHB(2F,3F)-O2 (4-6) 3%

The composition having negative dielectric anisotropy was prepared, andcharacteristics thereof were measured: NI=75.7° C.; T_(c)<−20° C.;Δn=0.100; Δ∈=−3.0; Vth=2.24 V; η=22.5 mPa·s.

To the composition, compound (1-1-1) was added at a ratio of 0.2% by theweight, and VHR-c was measured. VHR-c=81.0%.

The compositions in Example 1 to Example 13 were found to have a largevoltage holding ratio after irradiating with ultraviolet light incomparison with the composition in Comparative Example 1. Accordingly,the liquid crystal composition according to the invention is concludedto have superb characteristics.

INDUSTRIAL APPLICABILITY

A liquid crystal composition of the invention satisfies at least one ofcharacteristics such as a high maximum temperature, a low minimumtemperature, a small viscosity, a suitable optical anisotropy, a largenegative dielectric anisotropy, a large specific resistance, a highstability to ultraviolet light, a high stability to heat or the like, orhas a suitable balance regarding at least two of the characteristics. Aliquid crystal display device including the composition hascharacteristics such as a short response time, a large voltage holdingratio, a low threshold voltage, a large contrast ratio, a long servicelife and so forth, and thus can be used for a liquid crystal projector,a liquid crystal television and so forth.

1. A liquid crystal composition that has a negative dielectricanisotropy and a nematic phase, and contains at least one compoundselected from the group of compounds represented by formula (1) as anadditive, and at least one compound selected from the group of compoundsrepresented by formula (2) as a first component:

wherein, in formula (1) and formula (2), R¹ and R² are independentlyhydrogen or alkyl having 1 to 15 carbons; R³ and R⁴ are independentlyalkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons, alkenylhaving 2 to 12 carbons or alkenyloxy having 2 to 12 carbons; ring A andring C are independently 1,4-cyclohexylene, 1,4-cyclohexenylene,1,4-phenylene, 1,4-phenylene in which at least one of hydrogen isreplaced by fluorine or chlorine, or tetrahydropyran-2,5-diyl; ring B is2,3-difluoro-1,4-phenylene, 2-chloro-3-fluoro-1,4-phenylene,2,3-difluoro-5-methyl-1,4-phenylene, 3,4,5-trifluoronaphthalene-2,6-diylor 7,8-difluorochroman-2,6-diyl; Z′ is alkylene having 1 to 20 carbons,and in the alkylene, at least one of hydrogen may be replaced byhalogen, and at least one of —CH₂— may be replaced by —O—; Z² and Z³ areindependently a single bond, ethylene, methyleneoxy or carbonyloxy, whenall of Z² are a single bond, R³ is alkenyl having 2 to 12 carbons oralkenyloxy having 2 to 12 carbons; and a is 1, 2 or 3, b is 0 or 1, anda sum of a and b is 3 or less.
 2. The liquid crystal compositionaccording to claim 1, wherein a ratio of the compound represented byformula (1) is in the range of 0.005% by weight to 1% by weight based onthe weight of the liquid crystal composition.
 3. The liquid crystalcomposition according to claim 1, containing at least one compoundselected from the group of compounds represented by formulas (2-1) to(2-12) as the first component:

wherein, in formula (2-1) to formula (2-12), R⁴ and R⁵ are independentlyalkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons, alkenylhaving 2 to 12 carbons or alkenyloxy having 2 to 12 carbons; and R⁶ isalkenyl having 2 to 12 carbons or alkenyloxy having 2 to 12 carbons. 4.The liquid crystal composition according to claim 1, wherein a ratio ofthe first component is in the range of 10% by weight to 90% by weightbased on the weight of the liquid crystal composition.
 5. The liquidcrystal composition according to claim 1, containing at least onecompound selected from the group of compounds represented by formula (3)as a second component:

wherein, in formula (3), R⁷ and R⁸ are independently alkyl having 1 to12 carbons, alkoxy having 1 to 12 carbons, alkenyl having 2 to 12carbons, or alkenyl having 2 to 12 carbons in which at least one ofhydrogen is replaced by fluorine; ring D and ring E are independently1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene or2,5-difluoro-1,4-phenylene; Z⁴ is a single bond, ethylene orcarbonyloxy; and c is 1, 2 or
 3. 6. The liquid crystal compositionaccording to claim 5, containing at least one compound selected from thegroup of compounds represented by formulas (3-1) to (3-13) as the secondcomponent:

wherein, in formula (3-1) to formula (3-13), R⁷ and R⁸ are independentlyalkyl having 1 to 12 carbons, alkoxy having 1 to 12 carbons, alkenylhaving 2 to 12 carbons, or alkenyl having 2 to 12 carbons in which atleast one of hydrogen is replaced by fluorine.
 7. The liquid crystalcomposition according to claim 5, wherein a ratio of the secondcomponent is in the range of 10% by weight to 90% by weight based on theweight of the liquid crystal composition.
 8. The liquid crystalcomposition according to claim 1, containing at least one compoundselected from the group of compounds represented by formula (4) as athird component:

wherein, in formula (4), R⁹ and R¹⁰ are independently alkyl having 1 to12 carbons or alkoxy having 1 to 12 carbons; ring F and ring I areindependently 1,4-cyclohexylene, 1,4-cyclohexenylene, 1,4-phenylene,1,4-phenylene in which at least one of hydrogen is replaced by fluorineor chlorine, or tetrahydropyran-2,5-diyl; ring G is 2,3-difluoro-1,4-phenylene, 2-chloro-3-fluoro-1,4-phenylene,2,3-difluoro-5-methyl-1,4-phenylene, 3,4,5-trifluoronaphthalene-2,6-diylor 7,8-difluorochroman-2,6-diyl; and d is 1, 2 or 3, e is 0 or 1, and asum of d and e is 3 or less.
 9. The liquid crystal composition accordingto claim 8, containing at least one compound selected from the group ofcompounds represented by formulas (4-1) to (4-11) as the thirdcomponent:

wherein, in formula (4-1) to formula (4-11), R⁹ and R¹⁰ areindependently alkyl having 1 to 12 carbons or alkoxy having 1 to 12carbons.
 10. The liquid crystal composition according to claim 8,wherein a ratio of the third component is in the range of 5% by weightto 70% by weight based on the weight of the liquid crystal composition.11. The liquid crystal composition according to claim 1, wherein amaximum temperature of a nematic phase is 70° C. or higher, an opticalanisotropy (measured at 25° C.) at a wavelength of 589 nanometers is0.08 or more and a dielectric anisotropy (measured at 25° C.) at afrequency of 1 kHz is less than −2.
 12. A liquid crystal display device,including the liquid crystal composition according to claim
 1. 13. Theliquid crystal display device according to claim 12, wherein anoperating mode in the liquid crystal display device includes an IPSmode, a VA mode, a PSA mode, an FFS mode or an FPA mode, and a drivingmode in the liquid crystal display device includes an active matrixmode.
 14. (canceled)
 15. The liquid crystal composition according toclaim 5, containing at least one compound selected from the group ofcompounds represented by formula (4) as a third component:

wherein, in formula (4), R⁹ and R¹⁰ are independently alkyl having 1 to12 carbons or alkoxy having 1 to 12 carbons; ring F and ring I areindependently 1,4-cyclohexylene, 1,4-cyclohexenylene, 1,4-phenylene,1,4-phenylene in which at least one of hydrogen is replaced by fluorineor chlorine, or tetrahydropyran-2,5-diyl; ring G is 2,3-difluoro-1,4-phenylene, 2-chloro-3-fluoro-1,4-phenylene,2,3-difluoro-5-methyl-1,4-phenylene, 3,4,5-trifluoronaphthalene-2,6-diylor 7,8-difluorochroman-2,6-diyl; and d is 1, 2 or 3, e is 0 or 1, and asum of d and e is 3 or less.